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Network Working Group
Request for Comments: 1323
Obsoletes: RFC 1072, RFC 1185

V. Jacobson
LBL
R. Braden
ISI
D. Borman
Cray Research
May 1992

### TCP Extensions for High Performance

### Status of This Memo

This RFC specifies an IAB standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "IAB Official Protocol Standards" for the standardization state and status of this protocol. Distribution of this memo is unlimited.

### Abstract

This memo presents a set of TCP extensions to improve performance over large bandwidth*delay product paths and to provide reliable operation over very high-speed paths. It defines new TCP options for scaled windows and timestamps, which are designed to provide compatible interworking with TCP's that do not implement the extensions. The timestamps are used for two distinct mechanisms: RTTM (Round Trip Time Measurement) and PAWS (Protect Against Wrapped Sequences). Selective acknowledgments are not included in this memo.

This memo combines and supersedes RFC-1072 and RFC-1185, adding additional clarification and more detailed specification. Appendix C summarizes the changes from the earlier RFCs.

### Table of Contents

1. INTRODUCTION
2. TCP WINDOW SCALE OPTION

2.1 Introduction
2.2 Window Scale Option
2.3 Using the Window Scale Option

3. RTTM: ROUND-TRIP TIME MEASUREMENT

3.1 Introduction
3.2 TCP Timestamps Option
3.3 The RTTM Mechanism
3.4 Which Timestamp to Echo

4. PAWS: PROTECT AGAINST WRAPPED SEQUENCE NUMBERS

4.1 Introduction
4.2 The PAWS Mechanism

4.2.1 Basic PAWS Algorithm
4.2.2 Timestamp Clock
4.2.3 Outdated Timestamps
4.2.4 Header Prediction

4.3. Duplicates from Earlier Incarnations of Connection

5. CONCLUSIONS AND ACKNOWLEDGMENTS
6. REFERENCES
APPENDIX A: IMPLEMENTATION SUGGESTIONS
APPENDIX B: DUPLICATES FROM EARLIER CONNECTION INCARNATIONS

B.1 System Crash with Loss of State
B.2 Closing and Reopening a Connection

APPENDIX C: CHANGES FROM RFC-1072, RFC-1185
APPENDIX D: SUMMARY OF NOTATION
APPENDIX E: EVENT PROCESSING
Security Considerations
Author's Addresses

Original text document

Next: 1. INTRODUCTION

Connected: An Internet Encyclopedia
RFC 1323